The Health Effects of Air Pollution: The Human Body Under Attack

January 05, 2005 By Vicki Wolf, Citizens League for Environmental Action Now

The human body is an amazingly complex defense and self-healing system. The nose, mouth and throat filter air, food and water as it comes into the body. The skin, the largest organ of the body, protects the internal system from knocks, scrapes and cuts; senses changes in the environment; controls the body temperature; acts as a waterproof barrier and a screen against the sun's damaging radiation; and protects underlying tissues from infection. The brain and nervous system direct interpretation and reaction to sensations from the environment outside the body, internal organs, tissues and cells. The body has its own fight or flight mechanism that engages quickly when danger is near. If bacteria, viruses or other toxic enemies invade the body, white blood cells come to the body's defense and kill the invader. This intricate system of protection is increasingly under attack. The invader, which can be odorless and invisible, rides quietly on the most essential element in the human environment- the air we breathe. Air pollution -- toxins, particulate matter and ozone -- is the invader that can break down the body's defenses, or at least contribute to the burden this elegant defense system bears.

The Nose, Mouth and Throat
The main route for air pollutants is through the nose, mouth and throat. The nose is very efficient at trapping and holding some inhaled pollutants.

Concentrations of chemicals build up in the nose as the air is cleaned. The pollutants that accumulate in the nose can cause problems in the nose and sinuses or be absorbed in mucus membranes, resulting in a number of harmful effects on the body.

The cell damage caused by exposure to chemical pollutants puts the body's defense system on alert and initiates an inflammatory response, similar to an allergic response. This can cause immune suppression, making the body more susceptible to disease. It also can trigger a secondary immune response by causing the release of various chemicals or breakdown products. For example, when the nose is exposed to ozone, the airways are burned, causing inflammation and mucus production. The inflamed, runny nose has an increased sensitivity to allergens, such as pollen, and is more susceptible to viral and bacterial infections.

The Skin
The skin is a target organ for pollution and also the site of significant absorption of environmental pollutants. One of the main concerns for the health of the skin related to air pollution is skin cancer. Exposure to ultraviolet B (UVB) irradiation is closely associated with the development of skin cancers. Chemicals such as chlorofluorocarbons (CFCs) deplete the ozone layer allowing harmful amounts of UVB to penetrate to the earth's surface. Research shows that for a 1 percent decrease in stratospheric ozone (not to be confused with ground-level ozone), there will be a 2 percent increase in UVB irradiance and therefore, a 2 percent increase in skin cancer is likely.

The Blood
After air pollutants are inhaled, absorbed through the skin or the intestines, they can enter the blood stream, where their potential harmful effects are distributed throughout the body. Blood passes through all the body's organs and tissues, and can carry toxic substances as well as beneficial substances, such as oxygen, to them.

Chemicals with known adverse effects carried in the air include benzene, lead, mercury, carbon monoxide, volatile nitrites, pesticides and herbicides, and others. All of these have been found to lead to harmful effects on the blood as well as the system that is involved in the formation of blood including: blood cells, bone marrow, spleen, lymph nodes and the netlike system of cells that clean out foreign particles and infectious microorganisms.

Some air pollutants interfere with the function of blood, which results in detrimental effects on all organs of the body. For example, hemoglobin is the part of the red blood cell that carries oxygen from the lungs to the tissues of the body. Carbon monoxide, a product of incomplete combustion, binds over 200 times more firmly to hemoglobin than oxygen, seriously interfering with blood's oxygen-transport capability. Severe acute exposure can result in death due to asphyxiation or to permanent damage to the central nervous system.

The Lungs
A review of "Air pollution and health" in the October 2002 issue of Lancet describe a long list of short- and long-term studies showing an association between air pollutants and an increase in deaths and hospital admissions due to respiratory and cardiovascular disease. Ground-level ozone, nitrogen oxide and airborne particles are the main sources of concern. All three are oxidants, or oxygen free radicals. These unstable molecules are constantly released during metabolism, when the body's infection fighting cells are gobbling up and digesting bacteria, debris and foreign antigens. They are a part of normal metabolism and have other beneficial roles in the human body. But when oxidant air pollutants are brought into this mix, cell damage occurs causing inflammation and making cells more vulnerable to cancer.

Severe inflammation can cause significant damage including scarring of lung tissue, called fibrosis, and abnormal thickening. These disorders make breathing more difficult.

In addition to causing inflammation in the lung, ground-level ozone has been shown to contribute to hyper-responsiveness to allergens and mucus production that exacerbates asthma and may cause asthma in children.

Nitrogen oxide impairs the infection-fighting ability of white blood cells in the alveoli- thin walled sacs at the end of the bronchi deep in the lung- and therefore may increase the risk of lung infections.

Inhalation of particulate matter that is 2.5 microns in diameter and smaller (PM2.5) doesn't appear to harm the larger passages of the lung, but does injure the deeper, smaller thin-walled bronchioles where the body begins to extract oxygen from air. The tiny airborne particles can lodge permanently in the lung and cause free radical damage that leads to inflammation of the tissue lining the lungs, tissue damage and damage to macrophages -- white blood cells responsible for clearing away debris of the alveoli. Airway inflammation also may occur.

Recent studies show that ultrafines- airborne particles that are less than 0.1 microns in diameter (PM0.1)- are 10 to 50 times as potent as PM2.5-PM10 in inducing oxidant damage. They also are able to carry more toxic hydrocarbons, metals and other toxins on their surface, per unit mass, than larger particles.

Exposure to toxic chemicals from incinerators, power plants, mining operations and other industrial facilities also have been linked to lung cancer. Volatile organic compounds, nitrogen-containing and halogenated organics, PAH's (polycyclic aromatic hydrocarbons), toxic metals and many byproducts of incomplete combustion are all potential carcinogens that pollute the air. Often in air pollution there is the very unhealthy combination of oxidants damaging cells and making them more vulnerable to cancer and the exposure to these carcinogens.

The Cardiovascular System
While it is expected that dirty air and fine particles of dust would cause damage to the lungs and breathing problems, some researchers are reporting that the worst effects of air pollution are on the cardiovascular system.

According to the American Heart Association, air pollutants can cause the blood to become thick, increasing its tendency to clot, damaging arteries and promoting atherosclerosis - a buildup of fatty deposits in vessel walls.

New studies are revealing that exposure to high concentrations of PM2.5, carrying metals and hydrocarbons, increases the production of endothelin, a protein that regulates blood pressure by telling blood vessels when they need to constrict. This surge of endothelin does not seem to harm healthy people. But those who have artery-clogging atherosclerosis are at higher risk of dying after a heart attack if exposed to higher levels of endothelin - 150 micrograms per cubic meter (micrograms/m3) - a range typical in highly polluted cities such as Houston and Los Angeles.

The Brain
It is now known that ultrafine particles are small enough to get past the blood-brain barrier, the membrane between circulating blood and the brain that prevents damaging substances from reaching brain tissue and cerebrospinal fluid.

A study involving 200 dogs in Mexico City found that exposure to ultrafine particles carrying metals associated with fossil fuel combustion causes brain damage. Neuropathologist Lilian Calderon-Garcideunas found such metals - vanadium and nickel - in the dogs' nasal tissue and in their brains. Dogs at age 10 and older had waxy brain plaque like that found in people who have Alzheimer's Disease. The connection is alarming because the researchers also examined the nasal passages of people in Mexico City and found evidence of a breakdown of nasal tissue, similar to that found in the dogs.

Neuroblastoma, brain tumors and nervous system tumors have been linked to environmental carcinogens.

How to Protect Your Health
With the increase in allergies, asthma, cancer, cardiovascular disease and Alzheimer's Disease over the past decade, it is important to know that there are steps you can take to protect your health and the health of your family. Oxidants, or free radicals, are a recurring villain in the story of air pollution and health. Studies are showing that antioxidants may help your body stay in balance during the daily ravages of this villain.

Follow a Diet High in Antioxidants
A healthy, well-balanced diet that avoids toxins, such as nitrates and pesticides, and is high in antioxidants can help you stay well.

Antioxidants help the body clear oxidants away before cell injuries can occur. They also inhibit enzymes that cause cancer, and help the body repair the damage done by oxidants. There are many antioxidants including folic acid and vitamin C. Green tea and foods high in vitamin E are excellent sources of antioxidants.

Green tea is better than black tea because it is less processed and contains higher levels of antioxidants. Steeping the tea for about five minutes releases over 80 percent of the antioxidants in tea - called catechins.

The most active ingredient in vitamin E is the antioxidant known as alpha-tocopherol. Foods high in vitamin E include vegetable oils, nuts and green leafy vegetables. You can find out more about vitamin E at the National Institutes of Health website.

Relax, Meditate to Calm Your Immune System
Exposure to air pollution revs up your immune system to a point of being out of balance. It may be possible to relieve allergy symptoms and calm the immune system through deep relaxation. Jeff Migdow, M.D., holistic physician at the Kripalu Center for Yoga & Health in Lenox, Massachusetts told Yoga Journal: "Relaxation diminishes fight-or-flight response and thereby reduces allergic symptoms." He explained that during relaxation the nervous system tells the immune system to calm down or back off. When this happens, inflammation and mucus decrease and symptoms subside.

A 1997 study by neuroscientist Richard Davidson and Jon Kabat-Zinn, author and founder of the Stress Reduction Clinic at the University of Massachusetts Medical School, found that volunteers who took an eight-week meditation course had a more robust ability to produce antibodies in response to receiving a flu vaccine.


For more information, contact:

Geoffrey Castro
Executive Director
Citizens League for Environmental Action Now
Telephone: (713) 524-3000